[gmx-users] g_angle and a dihedral

[Vitaly V. Chaban]

I compute a dihedral using g_angle.

g_angle -h:
It should be noted that the index file must contain atom triplets for angles
or* atom quadruplets for dihedrals*. If this is not the case, the program
will
crash.

I get:

Program g_angle_mpi, VERSION 4.6.1
Source code file: /root/workdir_kn/gromacs-4.6.1/src/tools/gmx_angle.c,
line: 228

Fatal error:
number of index elements not multiple of 3, these can not be angle triplets

For more information and tips for troubleshooting, please check the GROMACS
website at http://www.gromacs.org/Documentation/Errors

My index.ndx:
[ angles ]
16 8 7 46

Is it healable?